UPDATE 2-Gunmen kidnap 8 from Exxon oil platform off Nigeria

* Exxon: armed men boarded offshore facility

* Eight Nigerian crew kidnapped, security source says

* Platform is one of eight in Exxon’s Oso field

(Adds abductions, details of field)

By Nick Tattersall

LAGOS, Nov 15 (Reuters) - Gunmen attacked an Exxon Mobil oil platform off the Nigerian coast late on Sunday, kidnapping eight Nigerian crew members in the second such raid in the region in a week.

The U.S. energy firm said armed men boarded the offshore facility, operated by its Mobil Producing Nigeria arm in a joint venture with the state-run Nigerian National Petroleum Corporation (NNPC), but initially gave no further details.

A security source said eight local crew members were kidnapped during the attack on the platform by gunmen in speedboats in the Oso field off the southern state of Akwa Ibom, one of Nigeria’s biggest condensate fields.

“Relevant government and security agencies have been informed and appropriate response measures are under way at this time,” Exxon said in a statement on Monday.

Akwa Ibom is one of the states in the Niger Delta, a vast wetlands area containing onshore and offshore facilities that make up Africa’s biggest oil and gas industry.

Exxon did not say whether the attack had any effect on output. There are eight platforms in the Oso field, which averages output of around 75,000 barrels per day (bpd).

Oil companies in the region suffered years of attacks -- which at their peak were costing the OPEC member $1 billion in lost oil revenues -- until an amnesty programme began last August, buying more than a year of relative peace.

But the militants were always divided, and although many of the field commanders agreed to lay down their weapons, new leaders have started to emerge, security experts say.

Militants attacked a rig operated by exploration firm Afren in the same waters off Akwa Ibom a week ago, kidnapping two Americans, two Frenchmen, two Indonesians and a Canadian.

That attack was claimed by the Movement for the Emancipation of the Niger Delta (MEND), the main militant group in the region, which has threatened further strikes against energy facilities.

A resurgence in violence would embarrass President Goodluck Jonathan, the first head of state from the Niger Delta, who faces a tough battle in elections due in April.

Jonathan brokered last year’s amnesty, seen as one of the main achievements of his administration.

The military threatened on Saturday to raid camps of criminal gangs in the creeks of the Niger Delta, and told civilians in the vicinity to leave.

A major offensive by the armed forces would be the first in the Niger Delta since the amnesty began last August. (For more Reuters Africa coverage and to have your say on the top issues, visit: ) (Editing by Tim Pearce)